Sick leave after arthroscopic meniscus repair vs. arthroscopic partial meniscectomy

Objective To evaluate sick leave after meniscal repair vs arthroscopic partial meniscectomy (APM) and, for comparison, vs the general population. Method Using Swedish register data we included all employed persons aged 19–49 years in the general population of Skåne region and identified those having had meniscus repair or APM in the period of 2005–2012. We retrieved data on sick leave during 1 year before until 2 years after surgery. We used logistic regression to estimate the risk differences of being on sick leave and negative binomial model to analyze differences in the number of days on sick leave. Results We included 192 persons with meniscus repair, 2481 with APM, and 376 345 references without meniscus surgery. Of these, 55% of meniscus repair group, 43% of APM group had any sick leave in the 2-year period following the surgery, while 17% of the references were on sick leave in the corresponding period. The mean (SD) number of days of sick leave after meniscus repair was 55 (77) days and for APM 37 (86) days. Meniscus repair was associated with higher probability of sick leave compared to APM with an adjusted risk difference of 0.13 (95% CI 0.07–0.19). Conclusion Persons undergoing meniscus repair have more frequent and 37% longer periods of sick leave in the short term than persons undergoing APM. However, sick leave in the long-term warrant further attention as successful repair may be associated with less knee osteoarthritis development than APM.


Introduction
Acute meniscus tear is a common knee injury, with an incidence around 70/100 000 [1]. During most of the later part of 20th century arthroscopic partial meniscectomy (APM) has been the treatment of choice for meniscus tears, but during the 21st century meniscus repair has become increasingly frequent when repair is possible [2][3][4]. It is generally considered that suture of the meniscus, with added postoperative ambulatory restrictions, results in longer absence from work than APM. Studies confirming this notion, however, are lacking. There are only a few smaller, single center studies dealing with return to sports in athletes after meniscus repair [5][6][7]. It has been estimated that meniscus repair surgery is more expensive than APM, taking into consideration the longer time in the operating room, longer rehab and cost of implants, even without adding the costs of prolonged work absence [8]. There is evidence that APM hastens progression of osteoarthritis [9,10], and meniscus repair has been reported to be more cost effective than APM, when focusing on the anticipated decreased risk of osteoarthritis development, increased quality of life and potentially less need for total knee arthroplasty [11].
There are a few studies describing sick leave after APM [12][13][14][15], but no direct comparisons with meniscus repair. Thus, our aim was to compare sick leave occurrence and duration in young and middle-aged patients undergoing APM or meniscal repair and relate these to sick leave in the general population in southern Sweden, which has a publicly financed social security system.

Ethics
The study was approved by the Ethics Committee (ethical approval IRBnumber: IRB_2011-432) and adheres to the rules of the Helsinki Declaration of 1975, as revised in 2000.

Register resources 2.2.1. Skåne healthcare register (SHR)
Within public healthcare in the Skåne region (population size 1 288 908, in the year 2014) all surgeries are recorded in the SHR. Private clinics do not report to the SHR, however, they did not perform meniscus repairs during this time period. From the register we retrieved surgical date, surgical type (Swedish version of NOMESCO Classification of Surgical Procedures; KKÅ97) and diagnostic codes registered according to the International Classification of Diseases, version 10 system [16]. The positive predictive value (PPV) of a surgical procedure code or an ICD10-code being correct in the register overall is 85-95%, with PPV for knee trauma and knee surgery being above 90% (90-92%) [17].

The population register
In Sweden all legal residents are included in the population register which is used for a variety of purposes by authorities and private corporations including tax agency, health care, banks etc. It is continuously updated with information on current residential address and deaths. From the register, we retrieved information on age, sex and residential area.

Swedish social security agency database (SSIA)
For employed persons, data is registered for all periods of sick leave that lasts longer than 14 days and that is reimbursed by the SSIA. The available data include personal identification number, dates of start and end of a sick leave period and extent of sick leave (25, 50 75 or 100%). Inhabitants in Sweden who cannot work, either because of illness or injury are entitled to sickness benefits (compensation for reduced income) counting from day 2 of a reported sickness period. For individuals with employment, day 2-14 is paid for by their employer. If the period of illness exceeds 14 days, it is thereafter reimbursed by the Swedish Social Insurance Agency (SSIA). If an individual is unemployed, on parental leave or a student, then SSIA registers and reimburses them from day 2 if they apply for the benefit. A smaller group of self-employed is reimbursed according to different rules. Around 76% of all the people in the SSIA register pertains to the group "employed", with the most homogenous data. Thus, in this study we only included employed persons and could only capture sick leave episodes with duration of at least 14 days.

Inclusion and exclusion criteria
We identified all male and female patients in the SHR having had APM (code NGD11) or meniscus suture (NGD21) with an ICD-10 diagnosis of meniscus injury (S83.2 or M23.2) during January 1, 2005 until December 31, 2012 in age interval 19-49 years old at the time of surgery, and registered resident in Skåne at the end of the year of surgery and one calendar year before the surgery date. As control group we identified all persons not having meniscal surgery (any NGD code), but having had at least one healthcare visit during January 1, 2005 until December 31, 2012, age interval 19-49 years old at the time of the visit, and registered resident in Skåne at the end of the year of inclusion and one calendar year before the year of the visit. For each person we randomly sampled one visit as the index date. We excluded a person, from all groups, if during 4 years preceding the inclusion date they were diagnosed with any of the following: fracture in the knee (ICD-10 code: S82.1, S82.9, S72.4 and 72.9), dislocation of knee (ICD-10 code: S83.1), rupture of Medial Collateral Ligament (MCL)/Lateral Collateral Ligament (LCL) (ICD-10 code: S83.4), diagnosis of knee osteoarthritis (ICD-10 code: M17.1-9), other meniscus surgery at index date (NGD20 or NGD22) previous meniscus surgery (surgery codes: NGD11-99, NGD21-99). Further, we excluded persons with disability pension (at the surgery/index date), sick leave in any form lasting the whole 360-day period before surgery/index date, since any prolonged sick leave on their part would probably not be attributed to the performed meniscus surgery. We excluded all patients with surgeries to the meniscus within 4 years prior, since we didn't have laterality, and this was a way to exclude re-operations to the same knee [18]. We also excluded all patients with diagnosed knee osteoarthritis, since they would have a very low probability of getting a meniscus repair which would make the groups less comparable. In Table 4 and Fig. 1 a summary of the inclusion and exclusion process is presented.

Surgical method
During the study period, all hospitals in the region for most cases used the same 2 portal arthroscopy technique (one work portal) and all-inside suture technique, except for some anterior horn meniscal repairs, where outside-in technique was employed. Patient were under general anesthesia. Whether a tourniquet was used or not during surgery was not recorded. However, previous research suggest that this does not significantly alter the length of return to work [19].

Postoperative regime
Standard postoperative care in southern Sweden after most common meniscus repair surgery includes walking with 2 crutches with full weightbearing during 6 weeks to normalize gait. Patients are prohibited to put wight to the knee with more flexion than 90 for 6 weeks post surgery. They are encouraged to neuromuscular rehabilitation of the knee under supervision by a physiotherapist until normal knee function is restored. All patients with high knee loading occupations are prescribed sick leave for up to 6 months to avoid putting the meniscal repair at risk to re-rupture. The same timeframe of 6 months is also the recommendation to avoid sports activities, especially with high knee loads in flexion and rotation.
After APM, standard postoperative care in Sweden is full weightbearing, 2 crutches for walking to normalize gait in some cases when needed, as well as rehabilitation of the knee supervised by a physiotherapist until normal knee function is restored. The rehabilitation and sick leave prescribed after APM surgery is governed by knee symptoms, and with work demanding high knee function, usually for 2-4 months.

Outcome definition and follow-up time
Our outcomes included a binary variable denoting if a person was on any sick leave longer than 14 days during the first two years after the surgery. Then, we also calculated number of net days on any sick leave during the initial 2 years after the surgery. Every day that a person received any amount of sick leave compensation (partial or full day), was counted as '1' day of sick leave.

Statistical analysis
We used logistic regression and the method of standardization to compute the risk ratio and risk differences of being on sick leave. Then, only among persons on sick leave, we fitted a negative binomial model with robust standard errors to estimate the ratio of mean number of days on sick leave between the groups. Both regression models were adjusted for age, sex, marital status, level of education, if born outside Sweden, and income. Further, as rupture of anterior crucial ligament is common in conjunction with a traumatic meniscal tear and associated with more serious surgery, and thus potentially longer sick leave, we adjusted the models for the presence of ACL surgery (codes NGE41) at the time of the surgery.
All statistical analyses were performed using IBM SPSS version 26, New Orchard Road, Armonk, New York, United States and Stata (Stata-Corp. 2021. Stata Statistical Software: Release 17. College Station, TX: StataCorp LLC.).

Results
Out of the general population of Skåne region of 1.3 million inhabitants, we identified 493 494 subjects fulfilling the inclusion criteria. A total of 379 018 subjects were included after applying our exclusion criteria (192 patients with meniscus repair, 2481 with APM and 376 345 reference subjects). (Table 1). During the two years after the surgery date, 55% in the repair group and 43% in the APM group had had any episode of sick leave longer than 14 days. Numbers for each subgroup is presented ( Table 2).
After adjusting for potential confounders, the risk ratio of being on sick leave for more than 14 days during the two years after surgery in patients undergoing meniscus repair compared to the general population was 3.6 (95% CI 3.3., 4.0), with corresponding risk difference of 0.45 (95% CI 0.38, 0.51). The corresponding estimates for APM was 2.6 (95% CI 2.5 to 2.7), and 0.27 (95% CI 0.25, 0.29), respectively. The adjusted comparison of meniscus repair with APM yielded a risk ratio of 1.8 (95% Table 2 The number of sick days specified in each group. APM ¼ arthroscopic partial meniscectomy; N/A ¼ non applicable. Among those on sick leave, the sick leave was on average 37% (95% CI 15%, 64%) longer after meniscus repair than APM.
We further adjusted for the presence of ACL rupture with or without concomitant ACL reconstruction in calculating the risk of being on sick leave for meniscus repair versus APM. The results were similar (Table 3).
To investigate if there was any sex-difference we calculated the adjusted risk difference for being on sick leave for meniscus repair versus APM to be 0.15 (95% CI 0.07, 0.22) for men and 0.10 (95% CI 0.00, 0.20) for women. Table 3: We illustrate the crude pattern (unadjusted for age and sex differences) of sick leave over time, both total numbers (Fig. 2) and after excluding ACL-reconstructions (Fig. 3). The meniscus repair-group had a higher percentage and longer duration of sick leave after surgery, but then over time return to a somewhat lower proportion on sick leave than the APM group.
The curve for sick leave after APM flattens out after the postoperative phase, but never returned to the preoperative levels, instead between 4 and 5% of patients remained on sick leave both 1 and 2 years postoperatively.

Discussion
We investigated the frequency and average length of sick leave longer than 14 days after meniscus repair and APM in southern Sweden during a 10-year time frame. Our findings reveal that both male and female patients after meniscus repair are on sick leave to a higher extent, and for longer periods of time than after APM. However, we found no clinically relevant sex differences in the propensity to be on sick leave after repair. Interestingly, this differs from the general pattern of women being on more and longer sick leave, both in the general population and after APM [15]. There was a minor difference in the number of patients working with high knee demand jobs between the APM and repair group. As expected, there were slightly more APMs in the group with high knee demands, since choosing an APM over a repair could be mainly a request from the patient after informed consent regarding meniscal surgical options and consequences. It could also be a result of this category having more complex degenerative tears not suitable for repair surgery.
The goals of meniscus surgery for a traumatic tear is to alleviate symptoms while still saving as much of the meniscus function as possible. It is well established that APM is associated with an increased risk of osteoarthritis, but also that meniscus suture repair has a higher risk of reoperations than APM. The decision of whether to perform meniscus surgery with repair, APM or with non-operative management, depends on several factors such as meniscal quality and tear type, concomitant knee injuries and osteoarthritis, occupation and knee-joint loading, as well as the individual skill and preferences of the surgeon.
Unfortunately we lack the specific reasons for the sick leave due to data not available in the register. However, we capture "all cause" reimbursed sick leave longer than 14 days in an entire population based on prospectively ascertained data, not patients' self reports. The agreement between retrospective self-reporting and high quality prospectively ascertained register data on sick leave duration has been found to be poor    [20]. The data also show all-cause sick leave for 2 years following surgery, to better include complications and reoperations, not only the initial injury and surgery. Further we have contrasted the extent of sick leave to the corresponding extent of sick leave in the background population, which is on average 9 days per year (range 5-12 days) during this period. While our aim was to compare sick leave associated with two different surgical procedures for traumatic meniscal tears, and the diagnosis of meniscus tear was confirmed by arthroscopy, we were concerned of not having a similarly high validity of the coding in patients not having surgery. Hence, we opted not to monitor a group of patients with a diagnosis of meniscal tear without having had knee surgery. Unfortunately, the SHR register does not cover information if the meniscal tear was, for instance, confirmed by MRI or if it was purely made on clinical examination in the patients without surgery. To get homogenous data, we included only people with an employment and the right to sick leave reimbursement from SSIA. Previous studies have suggested that the mean duration of sick leave is 9-17 days for APM, and more than one third of patients had more than 14 days of sick leave (in median 31 days) [12,13,15]. In a study by Von Essen et al. authors reported that the mean number of sick days (counting from injury, not surgery) in a cohort of ACL-surgeries without meniscus injury, to be 88.5 days (SD 50.2) [21]. This is in line with our findings, that after meniscus repair with concurrent ACL reconstruction, the number of sick days is longer than without ACL reconstruction (114 days vs 96 days).
Being on sick leave after surgery, is not only a cost for society, but also there is a substantial reduction in the patients' personal income [22]. Reducing the time spent away from work would be beneficial to both. This investigation of mapping the current sick leave after surgery could be the first step in this effort.
Finally, it would be interesting to compare the length of sick leave also with non-operatively treated meniscus tears. A recent RCT comparing meniscal surgery with exercise in this patient group has been published recently, and a similar dataset could be used for measuring sick leave as well as knee function [23]. Register-based research is otherwise difficult in non-operatively treated tears. They do not routinely visit the hospitals and are likely less captured with the correct diagnosis.

Conclusion
This study confirms the notion that meniscus repair without ACL reconstruction, is associated with more sick leave episodes longer than 14 days, than APM in the short term. However, the long-term consequences warrant further attention as successful repair may be associated with less knee osteoarthritis development [24], and thus less sick leave and societal costs later in life.

Author contributions
Fredrik Boric-Persson (Fredrik.boric-persson@med.lu.se) was involved in study conception and design, the data analysis, interpretation of results, drafted the manuscript and final approval. Responsible for the integrity of the whole article. Aleksandra Turkiewicz was involved in study design, retrieval of data and statistical data analysis, interpretation of results, manuscript revision and final approval. Paul Neuman was involved in interpretation of data, manuscript revision and final   approval. Martin Englund was involved in study conception and design, interpretation of results, manuscript revision and final approval.

Role of the funding source
This study was funded by the Swedish Research Council, the Greta and Johan Kock Foundation, the Swedish Rheumatism Association, the € Osterlund Foundation, and Governmental Funding of Clinical Research within the National Health Service (ALF). The funding sources had no role in the design, collection, and interpretation of the data or the decision to submit for publication.

Declaration of competing interest
No conflict of interests for any of the authors.